JP2014095402A - Electromagnetic clutch, and device and method for controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electromagnetic clutch that is improved in operability while suppressing power consumption.SOLUTION: There is provided an electromagnetic clutch 100 including: an armature 4 provided with two or more streaks of non-magnetic parts 41 and 42 differing in diameter and attached to a rotary shaft LO; a rotor 1 including a friction plate 13 opposed to the armature, the friction plate being provided with three streaks of non-magnetic parts 131-133 having different diameters so as not to be overlapped with the non-magnetic parts 41 and 42, the rotor rotating around the rotary shaft LO by external force; a stator 2 having an electromagnetic coil 3 applying a magnetic flux generated by power conduction to the friction plate 13 to allow the armature 4 to be fixedly attracted to the rotor 1; and a control device 30 for the electromagnetic coil. The control device 30 is provided with a magnetomotive force change circuit 10 for setting electromotive force of the electromagnetic coil 3 to be higher than electromotive force in a normal operation of the electromagnetic clutch 100 in response to a power conduction start command to the electromagnetic coil 3, and returning the electromotive force of the electromagnetic coil 3 to the electromotive force in the normal operation of the electromagnetic clutch 100 when the armature 4 is fixedly attracted to the rotor 1.

Description

  The present invention relates to an electromagnetic clutch that performs intermittent transmission of power using an electromagnet, an electromagnetic clutch control device, and an electromagnetic clutch control method.

  The electromagnetic clutch is used when power transmission is intermittently performed using an electromagnetic coil in a drive mechanism of a compressor of a vehicle air conditioner. An armature is fixed to the tip of the rotating shaft of the compressor, and a rotor driven by an engine or the like is attached to the rotating shaft adjacent to the armature via a bearing so that it can rotate with respect to the rotating shaft. It has become. A recess is formed in the rotor in a ring shape from the compressor side, and a stator including an electromagnetic coil is inserted into the recess with a gap between the recess and the inner wall. The armature can move to the rotor side. When the electromagnetic coil is energized, the armature is attracted to the rotor side and fixed to the rotor by the magnetic flux passing between the rotor and the armature. A friction plate is provided on the contact surface of the rotor with the armature. When the armature is fixed to the rotor, the rotation of the rotor is transmitted to the rotation shaft of the compressor via the armature, and the compressor rotates.

  Generally, an armature is separated into an inner armature and an outer armature by a slit that circulates in the circumferential direction, and the inner armature and the outer armature are connected by a connecting portion (bridge) that divides the slit into a plurality of portions in the circumferential direction. . On the other hand, the rotor that is magnetically coupled to the armature is provided with two slits in the circumferential direction so as not to overlap the armature slit, and the rotor is divided into the outer rotor, the central rotor, and the inner rotor by the two slits. Has been. The outer rotor and the central rotor and the central rotor and the inner rotor are connected by connecting portions that divide the slit into a plurality of portions in the circumferential direction. In the electromagnetic clutch having this structure, between the rotor and the armature, the first opposing surface of the inner rotor and the inner armature, the second opposing surface of the inner armature and the central rotor, the third opposing surface of the central rotor and the outer armature, and the outer armature There are four opposing surfaces of the fourth opposing surface of the outer rotor.

  Therefore, if the direction of the magnetic flux when the electromagnetic coil is energized is the direction from the inner side to the outer side of the rotor, the magnetic flux is blocked by the slit, so that the magnetic flux enters the inner armature from the inner rotor through the first facing surface. . Since the magnetic flux entering the inner armature is also blocked by the slit, it enters the central rotor through the second opposing surface, then enters the outer armature through the third opposing surface, and returns to the outer rotor through the fourth opposing surface. Come. In this way, the magnetic flux penetrates between the rotor and the armature in a path (magnetic path) of the inner rotor → inner armature → center rotor → outer armature → outer rotor so that the attractive force between the rotor and the armature becomes strong. .

  Further, the armature is provided with two slits in the circumferential direction, and the rotor is provided with three slits in the circumferential direction so as not to overlap the slits of the armature, so that the opposing surface between the armature and the rotor is 6 An electromagnetic clutch as a location has also been proposed (see, for example, Patent Document 1). An electromagnetic clutch having six opposing surfaces between the armature and the rotor requires only about 2/3 of the magnetic flux to obtain the same transmission torque when the electromagnetic coil is energized, compared to an electromagnetic clutch having four opposing surfaces. There is a feature and power consumption can be kept low. And if the amount of required magnetic flux is low, the thickness of the iron part which comprises the magnetic circuit of an electromagnetic coil can also be made thin, the electromagnetic clutch can be reduced in weight, and the fuel consumption performance of a vehicle improves.

  In the air gap between the rotor and the armature, the facing surface on which the magnetic path is formed is called an attracting surface or a magnetic pole. The facing surface has four electromagnetic clutches with double flux and the facing surface has six electromagnetic surfaces. The clutch is called a triple flux electromagnetic clutch. In the present application, hereinafter, a description will be given by assuming that a portion (opposing surface) where the magnetic flux crosses the air gap between the rotor and the armature is an opposing magnetic path.

JP 2005-344876 A

  As described above, the electromagnetic clutch can generate higher transmission torque when there are six opposing magnetic paths between the rotor and the armature than when there are four opposing magnetic paths. However, if the number of opposing magnetic paths between the rotor and the armature is increased to six or more, the magnetic path across the air gap between the rotor and the armature becomes longer. For this reason, the electromagnetic attraction force at the start of energization of the electromagnetic coil, that is, the operating attraction force for switching the electromagnetic clutch from the off state to the on state is small, and the operability (starting characteristics) of the electromagnetic clutch is deteriorated. there were.

  In view of the above problems, the present invention provides an electromagnetic clutch, an electromagnetic clutch control device, and an electromagnetic clutch control method that improve the starting characteristics of the electromagnetic clutch and improve the operability of the electromagnetic clutch while suppressing the power consumption of the electromagnetic clutch. It is to provide.

  An electromagnetic clutch (100) according to the present invention that solves the above-described problems is provided with an armature (at least two non-magnetic portions (41, 42) having different radii in the circumferential direction and attached to a rotating shaft (7)). 4) and a friction plate (8) facing the armature (4), and the friction plate (8) has a different radius in the circumferential direction so as not to overlap the non-magnetic portions (41, 42). Three non-magnetic portions (81, 82, 83) are provided, the rotor (1) that rotates with respect to the rotating shaft (7) by an external force, and a magnetic flux generated by energization is applied to the friction plate (8) to provide the armature. A stator (2) having an electromagnetic coil (3) for electromagnetically attracting (4) to the rotor (1) and a control device (30) for controlling energization of the electromagnetic coil (3); The device (30) opens the energization of the electromagnetic coil (3). When a command is issued, the magnetomotive force of the electromagnetic coil (3) is increased, and when the armature (4) is electromagnetically attracted and fixed to the rotor (1), the magnetomotive force of the electromagnetic coil (3) is increased during normal operation. A magnetomotive force changing means (10) for returning the magnetic force is provided.

  The control device (30) of the electromagnetic clutch (100) according to the present invention for solving the above-mentioned problems is provided with at least two non-magnetic portions (41, 42) having different radii in the circumferential direction, and the rotating shaft (7) The armature (4) attached to the armature (4) and the friction plate (8) facing the armature (4) are provided. The friction plate (8) has different radii in the circumferential direction so that the nonmagnetic portions (41, 42) At least three non-magnetic portions (81, 82, 83) that are not overlapped are provided, the rotor (1) that rotates with respect to the rotating shaft (7) by an external force, and the magnetic flux generated by energization is applied to the friction plate (8 ) And a control device (30) for an electromagnetic clutch (100) including a stator (2) having an electromagnetic coil (3) for electromagnetically attracting the armature (4) to the rotor (1). Energization start command to coil (3) is issued When the armature (4) is electromagnetically attracted and fixed to the rotor (1), the magnetomotive force of the electromagnetic coil (3) is returned to the magnetomotive force during normal operation. A magnetomotive force changing means (10) is provided.

  The method for controlling the electromagnetic clutch (100) according to the present invention for solving the above-described problems is provided with at least two non-magnetic portions (41, 42) having different radii in the circumferential direction and attached to the rotating shaft (7). The armature (4) and the friction plate (8) facing the armature (4) are provided, and the friction plate (8) has a different radius in the circumferential direction so as not to overlap the nonmagnetic portions (41, 42). The at least three non-magnetic portions (81, 82, 83) are provided, the rotor (1) is rotated with respect to the rotating shaft (7) by external force, and the magnetic flux generated by energization is applied to the friction plate (8). An electromagnetic clutch comprising a stator (2) having an electromagnetic coil (3) for electromagnetically attracting the armature (4) and fixing the armature (4) to the rotor (1), and a controller (30) for controlling energization of the electromagnetic coil (8). 100) control method, When an energization start command is issued to the coil (3), the controller (30) is operated to increase the magnetomotive force of the electromagnetic coil (3), and the armature (4) is electromagnetically attracted to the rotor (1). When fixed, the control device (30) is made to perform an operation of returning the magnetomotive force of the electromagnetic coil (3) to the magnetomotive force during normal operation.

  As a result, when an energization start command is issued to the electromagnetic coil of the electromagnetic clutch, a larger magnetomotive force than usual is given to the electromagnetic coil, so that a large electromagnetic attraction force is generated between the rotor and the armature. Therefore, the operability of the electromagnetic clutch can be improved when the engine is switched from the off state to the on state. After that, when the armature is attracted to the friction plate, the magnetomotive force of the electromagnetic coil is returned to the normal magnetomotive force, so that the power consumption of the electromagnetic coil can be suppressed.

  In addition, the code | symbol attached | subjected above is an example which shows a corresponding relationship with the specific embodiment as described in embodiment mentioned later.

(A) The block diagram which shows one Example of a structure of a car air conditioner system when the electromagnetic clutch of this invention is installed in the compressor (compressor) of the air conditioner (car air conditioner) for motor vehicles, (b) FIG. 5 is a partial configuration diagram showing a modified embodiment in which the control device shown in (a) is incorporated in an air conditioner computer (ECU). (A) The block diagram of one Example of the electromagnetic clutch containing the cross-sectional structure of the electromagnetic clutch of the 1st Embodiment of this invention attached to the compressor of the car air-conditioning system shown to Fig.1 (a), (b) ) Shows a configuration of a modified embodiment of the embodiment described in (a), and is a partial configuration diagram showing an embodiment in which a PWM control circuit is used instead of the DC-DC converter. It is the front view and sectional drawing of a rotor and an armature which show a slit arrangement and a connecting part position of a rotor provided with three slits, and an armature provided with two slits. (A) is an electromagnetic clutch having a single ring-shaped non-magnetic portion on the armature and two ring-shaped non-magnetic portions on the friction plate of the rotor, and the friction surface gap (the gap between the opposing magnetic paths) is 0 mm. (B) is a schematic cross-sectional view showing the state of the armature and rotor in the case (on), and (b) is the armature in the case where the gap between the opposed magnetic paths of the electromagnetic clutch shown in (a) is 0.5 mm (off). Schematic cross-sectional view showing the state of the rotor, (c) is an armature having two ring-shaped non-magnetic portions on the armature and three clutch-shaped non-magnetic portions on the friction plate of the rotor between the opposing magnetic paths. Schematic sectional view showing the state of the armature and rotor when the gap is 0 mm (when on), (d) is when the gap between the opposed magnetic paths of the electromagnetic clutch shown in (a) is 0.5 mm (when off) It is a schematic sectional drawing which shows the state of an armature and a rotor. 5 is a table showing a comparison of the number of opposing magnetic paths in the electromagnetic clutch shown in FIGS. 4A to 4D and the magnitude of the attractive force with respect to the magnetomotive force of the electromagnetic coil when ON and OFF → ON. FIG. 2A is a waveform diagram for explaining an example of the operation of the DC-DC converter shown in FIG. 2A, and FIG. 2B is a waveform diagram for explaining an example of the operation of the PWM control circuit shown in FIG. It is. (A) is a partial perspective view showing the structure on the rotor side when the armature of the electromagnetic clutch and the nonmagnetic part provided on the rotor are formed by ring-shaped slits, and (b) is the nonmagnetic part provided on the armature and rotor of the electromagnetic clutch. It is a fragmentary perspective view which shows the structure by the side of a rotor when a part is comprised with the ring-shaped member of a nonmagnetic material. When the number of opposed magnetic paths between the armature of the electromagnetic clutch and the rotor is 6, and when the nonmagnetic part provided in the armature and the rotor is formed by a slit and when it is configured by a nonmagnetic ring, when ON and OFF → ON It is a table which compares and shows the magnitude | size of the attractive force with respect to the magnetomotive force of the electromagnetic coil of. The block diagram of one Example of the electromagnetic clutch containing the cross-sectional structure of the electromagnetic clutch of the 2nd Embodiment of this invention attached to the compressor of the car air-conditioning system shown to Fig.1 (a), (b) is (a) FIG. 9 is a partial configuration diagram showing an embodiment in which a PWM control circuit is used instead of a DC-DC converter, showing a configuration of a modified embodiment of the embodiment explained in FIG. It is the front view and sectional drawing of a rotor and an armature which show a slit arrangement and a connecting part position of a rotor provided with four slits, and an armature provided with three slits.

  Hereinafter, embodiments of the electromagnetic clutch according to the present invention will be described with reference to the drawings. Here, as an example, an embodiment in which the electromagnetic clutch of the present invention is attached to an auxiliary machine of an automobile will be described.

  FIG. 1A shows an embodiment of a configuration of a car air conditioner system 80 in a case where an electromagnetic clutch 100 of the present invention is installed in a compressor 71 of a car air conditioner (car air conditioner) 70. Is. The car air conditioner 70 cools and dehumidifies the air in the passenger compartment to keep it comfortable, and includes a compressor 71, a condenser 72, a storage 73, an expansion valve 74, an evaporator 75, and a refrigerant passage 76 connecting them. Yes. The refrigerant sealed in the refrigerant passage 76 is compressed by the compressor 71 to be a high temperature / high pressure gas, cooled by the condenser 72 and liquefied, and then temporarily stored in the storage 73. The refrigerant coming out of the storage 73 becomes a low-pressure / low-temperature mist in the expansion valve 74, vaporized in the evaporator 75, takes heat from the surroundings, becomes a complete gaseous refrigerant, and returns to the compressor 71. In the car air conditioner 70, the air in the vehicle interior or the outside air is cooled by passing through the evaporator 75, and the temperature in the vehicle interior is adjusted by blowing the air into the vehicle interior by adjusting the temperature through a heater core provided separately.

  The compressor 71 is driven by the engine 60, and the belt 62 is stretched between the pulley 61 attached to the rotating shaft 67 of the engine 60 and the pulley 14 attached to the rotating shaft 7 of the compressor 71. Driven by. The electromagnetic clutch 100 transmits or blocks the rotation of the pulley 14 to or from the rotating shaft 7 of the compressor 71, and transmits the driving force of the engine 60 to the compressor 71 when the electromagnetic coil 3 is energized. When the 3 is not energized, the driving force of the engine 60 is cut off.

  The electromagnetic coil 3 is connected to the vehicle-mounted battery 38 through the control device 30 and the relay 39. When the relay 39 is turned on and the current value (magnetomotive force of the electromagnetic coil) is determined by the control device 30, the current from the battery 38 is It flows through the electromagnetic coil 3. The controller 30 is provided with a magnetomotive force changing circuit 10, and the magnetomotive force applied to the electromagnetic coil 3 can be changed by the magnetomotive force changing circuit 10. The relay 39 can be turned on / off and the magnetomotive force can be changed by the magnetomotive force changing circuit 10 by an air conditioner computer (ECU) 40 that issues a command indicated by a broken line to the relay 39 and the control device 30. If the magnetomotive force changing circuit 10 is provided separately from the ECU 40, the vehicle-side ECU need not be changed. Note that the control device 30 can be built in the ECU 40 as in the modified embodiment shown in FIG. + B indicates a + terminal (battery power supply) of the battery 38 shown in FIG.

  FIG. 2A shows an embodiment of the electromagnetic clutch 100 including a cross-sectional configuration of the electromagnetic clutch 100 according to the first embodiment of the present invention attached to the compressor 71 of the car air conditioner system 80 shown in FIG. The structure of an example is shown. The rotor 1 composed mostly of a magnetic material such as iron is fixed to a housing 77 of a compressor 71 through a bearing 6 so as to be freely rotatable. 79B is a retaining ring that fixes the bearing 6 to the housing 77 of the compressor 71. On the other hand, an inner hub 5 is fixed to the front end portion of the rotating shaft 7 of the compressor 71 by a bolt 15, and an outer hub 17 is attached to the outer peripheral portion of the inner hub 5 via a damper rubber 16. The armature 4, which is mostly made of a magnetic material, is fixed to the surface of the outer hub 17 on the rotor 1 side by a mounting member 19. The inner hub 5, the damper rubber 16, the outer hub 17 and the armature 4 rotate together with the rotating shaft 7. At this time, the armature 4 is elastically held by the action of the damper rubber 16 with respect to the inner hub 5 and can move to the rotor 1 side.

  In the rotor 1, the end plate on the armature 4 side is a friction plate 8, and the friction surface on the surface of the friction plate 8 is connected to and disconnected from the armature 4. The outer peripheral portion of the rotor 1 is the pulley 14 shown in FIG. 1A, and the belt V projections (not shown) are engaged with a plurality of V grooves provided in the pulley 14. On the other hand, the rotor 1 is formed with a ring-shaped recess 18 that opens to the housing 77 side of the compressor 71, and the rotor 1 has a U-shaped cross section. The stator 2 fixed to the housing 77 of the compressor 71 is inserted into the recess 18. There is a gap between the inner wall surface of the concave portion 18 of the rotor 1 and the stator 2, and the rotor 1 can rotate around the rotary shaft 7 without contacting the stator 2.

  The stator 2 includes an electromagnetic coil 3 wound in a ring-shaped spool 21, a yoke portion 22 provided around the spool 21, and a mounting plate 78 to which the yoke portion 22 is fixed. The ring 79A is fixed to the housing 77 of the compressor 71. The spool 21 is formed by resin molding using an electrically insulating resin as a constituent material. The yoke portion 22 of the stator 2 has a through hole 22a, and both end portions of the electromagnetic coil 3 are drawn out by the lead wire 31 through the through hole 22a, and one end is electrically grounded to the vehicle side. Is connected to the battery power source + B through the control device 30 and the relay 39. In this embodiment, a DC-DC converter 11 that boosts the voltage of the battery power source + B is built in the control device 30 as the magnetomotive force changing circuit 10. As the magnetomotive force changing circuit 10 applied to the electromagnetic coil 3, a PWM control circuit 12 shown in FIG. 2B can be used instead of the DC-DC converter 11.

  Further, the friction plate 8 on the armature 4 side of the rotor 1 according to the present invention has a nonmagnetic property as a magnetic blocker in order to link the magnetic flux generated by the electromagnetic coil 3 built in the stator 2 to the armature 4 side. Three or more ring-shaped slits having different radii are provided as parts. The friction plate 8 of this embodiment is provided with three ring-shaped slits 81, 82, 83 having different radii in order from the bearing 6 side. The friction plate 8 is divided into the first rotor portion 8A, the second rotor portion 8B, the third rotor portion 8C, and the fourth rotor portion 8D from the rotary shaft 7 side by the slits 81, 82, 83. When the slits 81, 82, and 83 are left as gaps, the first rotor portion 8A and the second rotor portion 8B, the second rotor portion 8B and the third rotor portion 8C, and the third rotor portion 8C and the fourth rotor portion 8D. Are connected to the slits 81, 82, 83. This connecting portion will be described later. Further, when the non-magnetic ring is formed by filling the gaps of the slits 81, 82, and 83 with a non-magnetic material such as copper or stainless steel, a connecting portion is unnecessary.

  Similarly, the armature 4 that is an annular plate-shaped member facing the friction plate 8 also has a ring-shaped slit as a non-magnetic portion that is a magnetic shielding portion in order to link the magnetic flux to the friction plate 8 side. Two or more strips are provided with different radii from the slits in the friction plate 8. The armature 4 of this embodiment is provided with two ring-shaped slits 41 and 42 having different radii in order from the rotating shaft 7 side. The armature 4 is divided into a first ring portion 4A, a second ring portion 4B, and a third ring portion 4C from the rotary shaft 7 side by the slits 41 and 42. When the slits 41 and 42 are left as gaps, in order to connect the first ring part 4A and the second ring part 4B and the second ring part 4B and the third ring part 4C, A connection is provided. This connecting portion will be described later. Further, when a nonmagnetic ring is formed by filling the gaps of the slits 41 and 42 with a nonmagnetic material such as copper or stainless steel, a connecting portion is not necessary.

  FIG. 3 shows a schematic configuration of the rotor 1 provided with the three slits 81, 82, 83 used in the present invention and the armature 4 provided with the two slits 41, 42. 42, the relationship between the slits 81, 82, 83 and the connecting portion will be described. As shown in FIG. 3, when the three slits 81, 82, 83 are provided in the rotor 1, three connection portions 85, 86, 87 are provided in each of the slits 81, 82, 83. In this embodiment, the connecting portions 85, 86, 87 are provided every 120 degrees with respect to the center of the rotor 1. However, the number and positions of the connecting portions 85, 86, 87 are limited to this embodiment. is not. The friction plate 8 is divided into the first rotor portion 8A, the second rotor portion 8B, the third rotor portion 8C, and the fourth rotor portion 8D from the inside by the slits 81, 82, 83.

  When the three slits 81, 82, 83 are provided in the rotor 1, the opposing armature 4 is provided with the slits 41, 42 at the portions facing the second rotor portion 8B and the third rotor portion 8C, respectively. . Accordingly, the radii of the slits 41 and 42 are different from the radii of the slits 81, 82, and 83. When the two slits 41 and 42 are provided in the armature 4, three connection portions 44 and 45 are provided in each of the slits 41 and 42. In this embodiment, the connecting portions 44 and 45 are provided every 120 degrees with respect to the center of the armature 4. The number and position of the connecting portions 44 and 45 are not limited to this embodiment. The armature 4 is divided into a first ring portion 4A, a second ring portion 4B, and a third ring portion 4C from the inside by the slits 41 and 42.

  In the rotor 1 and the armature 4 configured as described above, the first ring portion 4A faces the first rotor portion 8A and the second rotor portion 8B, and the second ring portion 4B becomes the second rotor portion 8B and the third rotor. The third ring portion 4C faces the third rotor portion 8C and the fourth rotor portion 8D. Thus, between the friction plate 8 and the armature 4 of the rotor 1, there are six pairs of opposing surfaces through which magnetic flux can pass, that is, opposed magnetic paths. In this configuration, the magnetic flux emitted from the first rotor portion 8A is, as indicated by a broken line, the first ring portion 4A → the second rotor portion 8B → the second ring portion 4B → the third rotor portion 8C → the third ring portion 4C. → Link the six opposing magnetic paths along the path of the fourth rotor portion 8D. If there are six opposing magnetic paths between the rotor 1 and the armature 4, a stronger attractive force is generated between the rotor 1 and the armature 4 than when there are only four locations. It is well known that the magnetomotive force applied to the electromagnetic coil can be reduced. This will be described with reference to FIGS.

  FIG. 4A shows a friction surface gap (opposing) of an electromagnetic clutch in which the armature 4 has a single ring-shaped nonmagnetic portion 41 and the friction plate 8 of the rotor 1 has two ring-shaped nonmagnetic portions 81 and 82. It is a schematic sectional drawing which shows the state of an armature and a rotor when the space | gap between magnetic paths is 0 mm (at the time of ON). FIG. 4B is a schematic cross-sectional view showing the state of the armature 4 and the rotor 1 when the gap between the opposed magnetic paths is 0.5 mm (when off) in the electromagnetic clutch shown in FIG. FIG. 4 (c) shows an opposing state of an electromagnetic clutch in which the armature 4 has two ring-shaped nonmagnetic portions 41, 42 and the friction plate 8 of the rotor 1 has three ring-shaped nonmagnetic portions 81, 82, 83. It is a schematic sectional drawing which shows the state of the armature 4 and the rotor 1 when the space | gap between magnetic paths is 0 mm (at the time of ON). FIG. 4D is a schematic cross-sectional view showing the state of the armature 4 and the rotor 1 when the gap between the opposing magnetic paths is 0.5 mm (when off) in the electromagnetic clutch shown in FIG. 4 (a) to 4 (d) correspond to the members indicated by the reference numerals described in FIG.

  FIG. 5 shows the number of opposing magnetic paths in the electromagnetic clutch shown in FIGS. 4 (a) to 4 (d) and the magnitude of the attractive force with respect to the magnetomotive force of the electromagnetic coil when on and off → on. It is a table. The magnetomotive force is an electric current for obtaining a necessary attractive force. As can be seen from FIG. 5, when the number of opposing magnetic paths is 4, the magnetomotive force for obtaining the attractive force 4000N at the on time is 680AT, and the magnetomotive force for obtaining the attractive force 200N at the off → on is 680AT. It is. On the other hand, when the number of opposed magnetic paths is 6, the magnetomotive force for obtaining the attractive force 4000N at the time of ON may be 410AT. Therefore, when the electromagnetic clutch is held in the on state, the magnetomotive force is smaller when the number of opposed magnetic paths is six.

  Next, with regard to the attractive force and magnetomotive force when the electromagnetic clutch is switched from the off state to the on state, when the number of opposing magnetic paths is 6, the magnetomotive force to obtain the attractive force 200N at the time of off to on is 810AT. When turned on with a magnetomotive force of 410 AT when turned on, an attractive force of only 50 N can be obtained. On the other hand, when the number of opposed magnetic paths is 4, turning off and turning on with the magnetomotive force 680AT at the time of turning on results in 200 N of attractive force, so when the number of opposed magnetic paths is 6, off → on It can be seen that the attractive force at that time is weaker than when the number of opposed magnetic paths is four. For this reason, in the case of an electromagnetic clutch having six opposing magnetic paths, when the electromagnetic coil is driven by the magnetomotive force at the time of turning on, the operating attractive force for turning the electromagnetic clutch from the off state to the on state is small. The operability (starting characteristics) of is deteriorated.

  Therefore, in the present invention, the magnetomotive force of the electromagnetic coil is increased by increasing the voltage applied to the electromagnetic coil when the electromagnetic clutch is turned on by the DC-DC converter 11 shown in FIG. FIG. 6A is a waveform diagram for explaining an embodiment of the operation of the DC-DC converter 11 shown in FIG. In this embodiment, when the electromagnetic clutch is turned on at time t0 when the electromagnetic clutch is off, the DC-DC converter 11 raises the battery voltage of 12V to, for example, 24V and applies it to the electromagnetic coil. Then, at time t1 when the armature of the electromagnetic clutch is attracted by the rotor and the gap becomes zero, the DC-DC converter 11 returns the voltage applied to the electromagnetic coil to the battery voltage of 12V. The time t1 when the armature of the electromagnetic clutch is attracted by the rotor and the gap becomes 0 can be detected by providing a sensor in the electromagnetic clutch, but usually a predetermined elapsed time from the detection of the signal for turning on the electromagnetic clutch Can be determined as The time for which the armature of the electromagnetic clutch is attracted to the rotor and the gap becomes 0 varies depending on the model, but is between 0.1 and 1 second, and may be determined according to the model.

  For example, when the number of turns of the electromagnetic coil is 203 turns (T) and the resistance value is 6Ω, when the electromagnetic coil is normally turned on, the power supply voltage is 12 V and a current of 2 A flows through the electromagnetic coil. The magnetic force is 2A × 203T = 406AT. On the other hand, when the electromagnetic coil is switched from the OFF state to the ON state, the power supply voltage is set to 24V, so that a current of 4A flows through the electromagnetic coil, and the magnetomotive force of the electromagnetic coil is 4A × 203T = 812AT. As a result, as in the case where the number of opposed magnetic paths shown in FIG. 5 is 4, an attractive force equal to the attractive force of 4000 N required when the electromagnetic clutch is turned on, and the attractive force equivalent to 200 N required when the electromagnetic clutch is turned on from off, Even when the number of opposed magnetic paths is 6, it can be obtained.

  Next, control when the PWM control circuit 12 shown in FIG. 2B is used will be described. The PWM control circuit 12 can change the magnetomotive force applied to the electromagnetic coil by intermittently applying the power supply voltage 12V to the electromagnetic coil and changing the duty ratio of the voltage applied to the electromagnetic coil. is there. FIG. 6B is a waveform diagram for explaining an embodiment of the operation of the PWM control circuit 12 shown in FIG. In this embodiment, when the electromagnetic clutch is turned on at time t0 when the electromagnetic clutch is in the off state, the duty ratio of the voltage applied to the electromagnetic coil is controlled by the PWM control circuit 12 to 100%. Then, at time t1 when the armature of the electromagnetic clutch is attracted by the rotor and the gap becomes zero, the duty ratio of the voltage applied to the electromagnetic coil is lowered by the PWM control circuit 12.

  For example, when the number of turns of the electromagnetic coil is 203 turns (T) and the resistance value is 3Ω, when the electromagnetic coil is turned from the off state to the on state, the power supply voltage is 12 V and the duty ratio is set to 100%. In this case, since a current of 4A flows through the electromagnetic coil, the magnetomotive force of the electromagnetic coil is 4A × 203T = 812AT. On the other hand, when the electromagnetic coil is normally turned on, the duty ratio is lowered so that a current of 2.3 A flows through the electromagnetic coil. In this case, since a current of 2.3A flows through the electromagnetic coil, the magnetomotive force of the electromagnetic coil is 2.3A × 203T = 421.09AT. As a result, as in the case where the number of opposed magnetic paths shown in FIG. 5 is 4, an attractive force equal to the attractive force of 4000 N required when the electromagnetic clutch is turned on, and the attractive force equivalent to 200 N required when the electromagnetic clutch is turned on from off, Even when the number of opposed magnetic paths is 6, it can be obtained.

  When the DC-DC converter 11 shown in FIG. 2 (a) is used when the number of turns of the electromagnetic coil is 203 turns (T) and the resistance value is 3Ω, 6V is applied to the electromagnetic coil when the electromagnetic clutch is turned on. And a voltage of 12 V may be applied from off to on.

  Here, the magnetic efficiency in the case where the connecting portion is provided in the slit provided in the rotor 1 and in the case where the resin nonmagnetic ring is embedded in the slit will be described. FIG. 7A illustrates the structure of the ring-shaped slit, and FIG. 7B illustrates the structure of a non-magnetic ring made of a non-magnetic material such as copper or stainless steel, which is filled in the slit. Is. For simplicity, FIGS. 7A and 7B show the case where the rotor is provided with two slits, but FIG. 8 shows the gap between the armature of the electromagnetic clutch and the rotor. The numerical value when the number of opposed magnetic paths is 6 is shown. As shown in FIG. 7A, the connecting portions 85 and 86 are bridges made of the same material as the rotor 1 that divides the ring-shaped slits 81 and 82 that are nonmagnetic portions provided in the rotor 1 of the electromagnetic clutch. It is. Further, as shown in FIG. 7B, the nonmagnetic ring 89 is a ring made of a nonmagnetic material such as copper or stainless steel, which is filled in ring-shaped slits 81 and 82 provided in the rotor 1 of the electromagnetic clutch. It is a member that connects both sides of the ring-shaped slits 81, 82. In the table shown in FIG. 8, the number of opposed magnetic paths between the armature of the electromagnetic clutch and the rotor is 6, and when the nonmagnetic part is formed by a slit and when the nonmagnetic part is formed by a nonmagnetic ring, The magnitude of the attractive force with respect to the magnetomotive force of the electromagnetic coil at the time of off to on is shown.

  As can be seen from FIG. 8, even when the number of opposed magnetic paths is 6, when the electromagnetic clutch is on, the slit is filled with a non-magnetic ring rather than the ring-shaped slit provided in the rotor is a gap. However, in order to obtain the same attractive force, the magnetomotive force applied to the electromagnetic coil is small. However, when the electromagnetic clutch is turned on from off, if the same magnetomotive force is applied to the electromagnetic coil as in the on state, the attractive force is 50 N when the ring-shaped slit is a gap, and 34 N when the ring is filled with a non-magnetic ring. And small. In order to obtain an attractive force of 200 N when the electromagnetic clutch is turned on from off, a magnetomotive force of 810AT is required when the ring-shaped slit is a gap, and a magnetomotive force of 850AT is required when the nonmagnetic ring is filled. is there.

  However, if the control is performed using the DC-DC converter 11 or the PWM control circuit 12 of the present invention shown in FIG. 2, even if the number of opposed magnetic paths is six, the ring-shaped slit provided in the rotor is not formed as a gap. It is possible to put to practical use an electromagnetic clutch filled with a non-magnetic ring. The electromagnetic clutch 100 including the DC-DC converter 11 or the PWM control circuit 12 of the present invention shown in FIG. 2 can be controlled even when the number of opposed magnetic paths is more than six.

  Therefore, an electromagnetic clutch 100A according to a second embodiment of the present invention in which the number of opposed magnetic paths is 8 will be described with reference to FIG. FIG. 9A shows an example of an electromagnetic clutch 100A including a cross-sectional configuration of the electromagnetic clutch 100A according to the second embodiment of the present invention attached to the compressor of the car air conditioner system shown in FIG. It is a block diagram. The electromagnetic clutch 100A of the second embodiment is different from the electromagnetic clutch 100 of the first embodiment only in the structure of the friction plate 8 and the armature 4 of the rotor 1, and the other structure is the electromagnetic clutch of the first embodiment. It is exactly the same as the clutch 100. Therefore, in the electromagnetic clutch 100A of the second embodiment, constituent members other than the friction plate 8 and the armature 4 are denoted by the same reference numerals as those of the electromagnetic clutch 100 of the first embodiment, and description thereof is omitted.

  In the electromagnetic clutch 100 of the first embodiment, in order to link the magnetic flux generated by the electromagnetic coil 3 built in the stator 2 to the friction plate 8 to the armature 4 side, the three strips having different radii in order from the bearing 6 side. Ring-shaped slits 81, 82, 83 were provided. The friction plate 8 is divided into the first rotor portion 8A, the second rotor portion 8B, the third rotor portion 8C, and the fourth rotor portion 8D from the rotary shaft 7 side by the slits 81, 82, 83. On the other hand, in the electromagnetic clutch 100A of the second embodiment, the friction plate 8 is provided with four ring-shaped slits 81, 82, 83, and 84 having different radii in order from the bearing 6 side. The friction plates 8 are moved from the rotary shaft 7 side to the first rotor portion 8A, the second rotor portion 8B, the third rotor portion 8C, the fourth rotor portion 8D, and the fifth rotor portion 8E by the slits 81, 82, 83, 84. It is divided.

  When the slits 81, 82, 83, and 84 are left as gaps, the first rotor portion 8A and the second rotor portion 8B, the second rotor portion 8B and the third rotor portion 8C, the third rotor portion 8C and the fourth rotor This is also the same in that connection portions are provided in the slits 81, 82, 83, 84 in order to connect the portion 8D, the fourth rotor portion 8D, and the fifth rotor portion 8E. When the non-magnetic ring is formed by filling the gaps of the slits 81, 82, 83, and 84 with a non-magnetic member such as copper or stainless steel, a connecting portion is unnecessary.

  On the other hand, the armature 4 of the first embodiment was provided with two ring-shaped slits 41 and 42 having different radii in order from the rotating shaft 7 side. The armature 4 is divided into the first ring portion 4A, the second ring portion 4B, and the third ring portion 4C from the rotary shaft 7 side by the slits 41 and 42. On the other hand, in the electromagnetic clutch 100A of the second embodiment, the armature 4 is provided with three ring-shaped slits 41, 42, 43 having different radii in order from the rotary shaft 7 side. The armature 4 is divided into the first ring portion 4A, the second ring portion 4B, the third ring portion 4C, and the fourth ring portion 4D from the rotary shaft 7 side by the slits 41, 42, and 43. When the slits 41, 42, 43 are left as gaps, the first ring portion 4A and the second ring portion 4B, the second ring portion 4B and the third ring portion 4C, and the third ring portion 4C and the fourth ring portion 4D. Are connected to the slits 41, 42, and 43. Further, when the non-magnetic ring is formed by filling the gaps of the slits 41, 42, and 43 with a non-magnetic member such as copper or stainless steel, a connecting portion is unnecessary.

  FIG. 9B shows a configuration of a modified example of one example of the electromagnetic clutch 100 </ b> A of the second embodiment described in FIG. 9A, and a PWM control circuit instead of the DC-DC converter 11. It is a partial block diagram which shows the Example in which 12 was used. Both the DC-DC converter 11 and the PWM control circuit 12 can be used in the electromagnetic clutch 100A of the second embodiment.

  FIG. 10 shows a schematic configuration of the rotor 1 provided with four slits 81, 82, 83, 84 and the armature 4 provided with three slits 41, 42, 43 used in the present invention. . FIG. 10 shows connection portions 44, 45, 46 in the slits 41, 42, 43 and connection portions 85, 86, 87, 88 in the slits 81, 82, 83, 64. When the four slits 81, 82, 83, 84 are provided in the rotor 1, three connection portions 85, 86, 87, 88 are provided in each of the slits 81, 82, 83, 84. In this embodiment, the connecting portions 85, 86, 87, 88 are provided every 120 degrees with respect to the center of the rotor 1. However, the number and positions of the connecting portions 85, 86, 87, 88 are the same as in this embodiment. It is not limited. The friction plate 8 is divided into the first rotor portion 8A, the second rotor portion 8B, the third rotor portion 8C, the fourth rotor portion 8D, and the fifth rotor portion 8E from the inside by the slits 81, 82, 83, 84. ing.

  When the four slits 81, 82, 83, 84 are provided in the rotor 1, the facing armature 4 has a portion facing the second rotor portion 8B, the third rotor portion 8C, and the fourth rotor portion 8D. Slits 41, 42, and 43 are provided, respectively. Therefore, the radii of the slits 41, 42, 43 are different from the radii of the slits 81, 82, 83, 84. When the three slits 41, 42, 43 are provided in the armature 4, three connection portions 44, 45, 46 are provided in each of the slits 41, 42, 43. In this embodiment, the connecting portions 44, 45, 46 are provided every 120 degrees with respect to the center of the armature 4. However, the number and positions of the connecting portions 44, 45, 46 are limited to this embodiment. is not. The armature 4 is divided into the first ring portion 4A, the second ring portion 4B, the third ring portion 4C, and the fourth ring portion 4D from the inside by the slits 41, 42, and 43.

  The first ring portion 4A is opposed to the first and third rotor portions 8A and 8B, the second ring portion 4B is opposed to the second and third rotor portions 8B and 8C, and the third ring portion 4C is third. The fourth rotor portion 8C and 8D are opposed to each other, and the fourth ring portion 4D is opposed to the fourth and fifth rotor portions 8D and 8E. As described above, there are eight opposing magnetic paths between the friction plate 8 of the rotor 1 and the armature 4, that is, eight opposing magnetic paths. In this configuration, the magnetic flux emitted from the first rotor portion 8A is, as indicated by a broken line, the first ring portion 4A → the second rotor portion 8B → the second ring portion 4B → the third rotor portion 8C → the third ring portion 4C. → Link the eight opposing magnetic paths in the path of the fourth rotor part 8D → the fourth ring part 4D → the fifth rotor part 8E.

  When there are eight opposing magnetic paths between the rotor 1 and the armature 4, the attraction force and magnetomotive force when the electromagnetic clutch is on and the attraction force and magnetomotive force when the electromagnetic clutch is switched from the off state to the on state are opposite. Similar to the case where there are six magnetic paths, the operability deteriorates. Therefore, even when there are eight opposing magnetic paths between the rotor 1 and the armature 4, the magnetomotive force is changed using the magnetomotive force changing circuit 10 such as the DC-DC converter 11 and the PWM control circuit 12 of the present invention, Control can be performed in the same manner as in the case of four opposing magnetic paths between the rotor 1 and the armature 4.

  In the above embodiment, the electromagnetic clutch 100 is applied to the compressor of the automotive air conditioner. However, the electromagnetic clutch of the present invention can be applied to other rotating devices as well. Therefore, the rotor 1 may be driven by another rotational drive source (for example, a motor) instead of driving the rotor 1 by power from the engine. The driven device to which the rotational force is transmitted via the electromagnetic clutch 100 may be other than the compressor.

  The above description is merely an example, and the present invention is not limited to the above-described embodiments and modifications unless the features of the present invention are impaired. The constituent elements of the embodiment and the modified examples include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. That is, other forms conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention. Moreover, it is also possible to arbitrarily combine one or more of the above-described embodiments and modified examples.

  As described above, according to the electromagnetic clutch, the electromagnetic clutch control device, and the electromagnetic clutch control method, when an energization start command is issued to the electromagnetic coil of the electromagnetic clutch, a larger magnetomotive force than usual is given to the electromagnetic coil. It is done. For this reason, when an energization start command is issued to the electromagnetic coil, a large electromagnetic attractive force is generated between the rotor and the armature, and the operability of the electromagnetic clutch is improved when the electromagnetic clutch is switched from the off state to the on state. Can do. After that, when the armature is attracted to the friction plate, the magnetomotive force of the electromagnetic coil is returned to the normal magnetomotive force, so that the power consumption of the electromagnetic coil can be suppressed.

DESCRIPTION OF SYMBOLS 1 Rotor 2 Stator 3 Electromagnetic coil 4 Armature 7 Rotating shaft 8 Friction plate 10 Magnetomotive force change circuit 30 Controller 35 Controller 100, 100A Electromagnetic clutch

Claims (16)

An armature (4) provided with at least two non-magnetic portions (41, 42) having different radii in the circumferential direction and attached to the rotating shaft (7);
A friction plate (8) facing the armature (4) is provided, and the friction plate (8) has a circumferential radius different so that it does not overlap the nonmagnetic portions (41, 42). A rotor (1) provided with nonmagnetic portions (81, 82, 83) of a strip and rotating with respect to the rotation shaft (7) by an external force;
A stator (2) provided with an electromagnetic coil (3) that applies magnetic flux generated by energization to the friction plate (8) and electromagnetically attracts the armature (4) to the rotor (1);
A control device (30) for controlling energization to the electromagnetic coil (3),
When an energization start command is issued to the electromagnetic coil (3), the control device (30) increases the magnetomotive force of the electromagnetic coil (3), the armature (4) is electromagnetically attracted, and the rotor ( An electromagnetic clutch comprising a magnetomotive force changing means (10) for returning the magnetomotive force of the electromagnetic coil (3) to the magnetomotive force during normal operation when fixed to 1).   The armature (4) has two non-magnetic portions (41, 42), and the rotor (1) has three non-magnetic portions (81, 82, 83). The electromagnetic clutch according to claim 1. The nonmagnetic part (41, 42, 81, 82, 83) is a slit,
The armature (4) includes a first ring portion (4A), a second ring portion (4B), and a third ring portion (4C) from the rotary shaft (7) side by the two slits (41, 42). The two slits are provided between the first ring part (4A) and the second ring part (4B) and between the second ring part (4B) and the third ring part (4C). (41, 42) are connected by a connection part (43, 44) that divides into a plurality of parts,
The rotor (1) has a first rotor portion (8A), a second rotor portion (8B), and a third rotor portion (from the rotary shaft (7) side) by the three slits (81, 82, 83). 8C) and a fourth rotor part (8D), and are divided between the first rotor part (8A) and the second rotor part (8B), the second rotor part (8B) and the third rotor part (8C). ) And the third rotor portion (8C) and the fourth rotor portion (8D) are connected by connecting portions (84, 85, 86) that divide the three slits (81, 82, 83) into a plurality of portions. The electromagnetic clutch according to claim 2, wherein the electromagnetic clutch is provided. The nonmagnetic part (41, 42, 81, 82, 83) is a nonmagnetic ring,
The armature (4) includes a first ring portion (4A), a second ring portion (4B), and a third ring portion (from the rotating shaft (7) side) by the two non-magnetic rings (41, 42). 4C), and between the first ring part (4A) and the second ring part (4B) and between the second ring part (4B) and the third ring part (4C), Are connected by non-magnetic rings (41, 42).
The rotor (1) includes a first rotor portion (8A), a second rotor portion (8B), and a third rotor from the rotating shaft (7) side by the three non-magnetic rings (81, 82, 83). Divided into a portion (8C) and a fourth rotor portion (8D), and between the first rotor portion (8A) and the second rotor portion (8B), the second rotor portion (8B) and the third rotor portion. (8C) and the third rotor portion (8C) and the fourth rotor portion (8D) are connected by the three non-magnetic rings (81, 82, 83). 2. The electromagnetic clutch according to 2.   The rotor (1) includes a ring-shaped recess (18) on the back side of the friction plate (8), and the electromagnetic coil (3) of the stator is disposed in the recess (18). The electromagnetic clutch according to any one of claims 1 to 4, wherein:   The magnetomotive force changing means (10) is configured such that when the armature (4) is electromagnetically attracted and fixed to the rotor (1), a time since the start of energization to the electromagnetic coil (3) is issued. The electromagnetic clutch according to any one of claims 1 to 5, wherein the determination is based on time.   The magnetomotive force changing means (10) gives a voltage to be applied to the electromagnetic coil (3) during normal operation of the electromagnetic clutch (100) when an energization start command is issued to the electromagnetic coil (3). A voltage applied to the electromagnetic coil (3) during normal operation of the electromagnetic clutch (100) when the armature (4) is electromagnetically attracted and fixed to the rotor (1). The electromagnetic clutch according to any one of claims 1 to 6, further comprising a voltage changing means (11) for returning to the position.   The magnetomotive force changing means (10) sets the duty ratio of the current supplied to the electromagnetic coil (3) when a command to start energization to the electromagnetic coil (3) is issued. The duty ratio of the current supplied to the electromagnetic coil (3) when the armature (4) is electromagnetically attracted and fixed to the rotor (1) is set higher than the duty ratio during operation. The electromagnetic clutch according to any one of claims 1 to 7, further comprising duty ratio changing means (12) for returning the duty ratio to the duty ratio during normal operation. An armature (4) provided with at least two non-magnetic portions (41, 42) having different radii in the circumferential direction and attached to the rotating shaft (7), and a friction plate (8) facing the armature (4) ), And the friction plate (8) has at least three nonmagnetic parts (81, 82, 83) that have different radii in the circumferential direction so as not to overlap the nonmagnetic parts (41, 42). The rotor (1) that rotates with respect to the rotating shaft (7) by an external force and a magnetic flux generated by energization are applied to the friction plate (8) to electromagnetically attract the armature (4) to the rotor ( 1) a control device (30) for an electromagnetic clutch (100) comprising a stator (2) comprising an electromagnetic coil (3) to be fixed to 1),
When an energization start command is issued to the electromagnetic coil (3), the magnetomotive force of the electromagnetic coil (3) is increased, and when the armature (4) is electromagnetically attracted and fixed to the rotor (1), An electromagnetic clutch control device comprising magnetomotive force changing means (10) for returning the magnetomotive force of the electromagnetic coil (3) to the magnetomotive force during normal operation.   The magnetomotive force changing means (10) is configured such that when the armature (4) is electromagnetically attracted and fixed to the rotor (1), a time since the start of energization to the electromagnetic coil (3) is issued. 10. The electromagnetic clutch control device according to claim 9, wherein the determination is made based on time.   The magnetomotive force changing means (10) gives a voltage to be applied to the electromagnetic coil (3) during normal operation of the electromagnetic clutch (100) when an energization start command is issued to the electromagnetic coil (3). A voltage applied to the electromagnetic coil (3) during normal operation of the electromagnetic clutch (100) when the armature (4) is electromagnetically attracted and fixed to the rotor (1). The electromagnetic clutch control device according to claim 9 or 10, further comprising voltage changing means (11) for returning to the above.   The magnetomotive force changing means (10) sets the duty ratio of the current supplied to the electromagnetic coil (3) when a command to start energization to the electromagnetic coil (3) is issued. The duty ratio of the current supplied to the electromagnetic coil (3) when the armature (4) is electromagnetically attracted and fixed to the rotor (1) is set higher than the duty ratio during operation. 11. The electromagnetic clutch control device according to claim 9, further comprising: a duty ratio changing means (12) for returning the duty ratio to a duty ratio during normal operation. An armature (4) provided with at least two non-magnetic portions (41, 42) having different radii in the circumferential direction and attached to the rotating shaft (7), and a friction plate (8) facing the armature (4) The friction plate (8) has at least three nonmagnetic portions (81, 82, 83) that have different radii in the circumferential direction so as not to overlap the nonmagnetic portions (41, 42). A rotor (1) that rotates with respect to the rotating shaft (7) by an external force; and a magnetic flux generated by energization is applied to the friction plate (8) to electromagnetically attract the armature (4) to the rotor (1). A control method of an electromagnetic clutch (100) including a stator (2) having an electromagnetic coil (3) to be fixed to the electromagnetic coil (8) and a control device (30) for controlling energization of the electromagnetic coil (8),
When an energization start command is issued to the electromagnetic coil (3), the controller (30) is caused to perform an operation of increasing the magnetomotive force of the electromagnetic coil (3),
When the armature (4) is electromagnetically attracted and fixed to the rotor (1), the controller (30) is caused to perform an operation of returning the magnetomotive force of the electromagnetic coil (3) to the magnetomotive force during normal operation. An electromagnetic clutch control method characterized by the above.   When the armature (4) is electromagnetically attracted and fixed to the rotor (1), the control device (30) is an elapsed time from when an energization start command is issued to the electromagnetic coil (3). 14. The electromagnetic clutch control method according to claim 13, wherein the determination is performed.   When the energization start command is issued to the electromagnetic coil (3), the control device (30) applies a voltage applied to the electromagnetic coil (3) from a voltage applied during normal operation of the electromagnetic clutch (100). When the armature (4) is electromagnetically attracted and fixed to the rotor (1), the voltage applied to the electromagnetic coil (3) is returned to the voltage applied during normal operation of the electromagnetic clutch (100). 15. The electromagnetic clutch control method according to claim 13 or 14, further comprising voltage changing means (11).   The controller (30) determines the duty ratio of the current supplied to the electromagnetic coil (3) when a normal operation of the electromagnetic clutch (100) is performed when an energization start command is issued to the electromagnetic coil (3). The duty ratio of the current supplied to the electromagnetic coil (3) when the armature (4) is electromagnetically attracted and fixed to the rotor (1) is set to be higher than the duty ratio of the electromagnetic clutch (100). 15. The electromagnetic clutch control method according to claim 13, further comprising duty ratio changing means (12) for returning the duty ratio to that during normal operation.

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